Energy distribution system



Jan. 16, 1968 s. c. JOHNSON 3,364,331

ENERGY DISTRIBUTION SYSTEM Filed Feb. 17, 1965 WITNESSES v INVENTOR m fW/MM Stewart C. Johnson ATTORNEY United States Patent Ofi ice 3,364,331 Patented Jan. 16, 1968 3,364,331 ENERGY DISTRIBUTION SYSTEM Stewart C. Johnson, Mansfield, Ohio, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 17, 1965, Ser. No. 433,340 4 Claims. (Cl. 219--10.55)

ABSTRACT OF THE DISCLOSURE A temperature responsive element in the form of a bimetallic structure, which structure is supported within the waveguide of a microwave oven and serves to vary the angle at which electromagnetic energy is introduced into the oven cavity from the waveguide thereby creating different operating modes.

This invention relates, in general, to domestic appliances such as microwave ovens and, more particularly, to means for uniformly distributing the microwave energy in the oven or similar enclosure.

Increases in temperature of materials exposed to electrom agnetic radiation in the microwave portion of the spectrum (from about 1000 to 300,000 megacycles per second, corresponding to wavelengths of from about 30 centimeters to l millimeter) are familiar phenomena. M-icrowave generators operating in the lower portion of this range are utilized to provide energy to cooking ovens or the like. This energy in the form of microwaves is usually transmitted to the interior of the oven through a wave guide. It is common knowledge that uniformity of heating of foodstuff in a microwave oven is largely dependent upon the number of field patterns or modes that are excited within the oven. Wave guides of the type presently being used in prior art devices are designed to transmit only one mode. If, therefore, food is placed in an oven utilizing this type of wave guide, there would be a cold spot at every half wavelength and between each pair of cold spots there would be a very hot spot. Although, in a multiplicity of modes, each mode would have its cold spots and more particularly its hot spots, the different hot spots would not impinge on the foodstuff in exactly the same place. Consequently, it is possible to obtain more uniform heating by providing a plurality of modes. The task then becomes one of exciting a sufficiently large number of modes to produce the desired heating uniforrn ity. Various means are presently employed to accomplish this result, the generally accepted means being the utilization of a rotating stirrer which both reflects the waves entering the oven at varying angles and, because of its metallic properties, creates areas in which the electric field is zero. The problems to be overcome in this type of arrangement are those of cost and space.

Accordingly, the general object of this invention is to provide a new and improved microwave oven.

It is a more particular object of this invention to provide a new and improved apparatus for effecting uniform distribution of energy in a microwave oven or the like.

Another object of this invention is to provide a new and improved means for uniformly distributing energy in a microwave oven which is inexpensive and requires a minimum amount of space.

Still another object of this invention is to provide means responsive to changes in temperature for varying the modes of energy in a microwave oven or the like.

Briefly, the present invention accomplishes the abovecited objects by providing a bimetallic element in the end of the Wave guide, used for conducting energy waves from a microwave energy source such as a magnetron. This bimetallic element replaces the conventional inclined surface usually employed to reflect the energy waves from the Wave guide into the interior of the oven in a horizontal plane and is adapted to excite different modes or reflect the microwave energy in varying directions as it expands and contracts under the influence of a resistance heating source which is periodically energized.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings in which:

FIGURE 1 is a side view, partly in section, of a range incorporating the invention; and

FIG. 2 is a sectional view taken on the line II-II of FIG. 1.

Referring to the drawings, especially FIG. 1, there is shown a cooking range generally indicated by reference character 10. A metallic enclosure or oven 11 mounted in the range is coupled to a microwave energy generator, for example, a magnetron 12, through a coupling wave guide 13. The magnetron may have a dome-shaped portion 14 which functions as an electromagnetic radiator of energy, conducted thereto from the magnetron cavity resonator. Such magnetrons, as Well as other types of magnetrons which are also adaptable for use herein, are well known in the art, therefore are not described in detail. While the wave guide and magnetron as illustrated are located at the rear of the oven, they may "be positioned in any convenient place, for example, in the bottom of the range immediately below the oven.

The coupling wave guide 13, through which energy emitted from the source 12 is transmitted, is provided with wave reflecting means 16, positioned in the path of energy waves and at substantially an angle of 45 With respect thereto to thereby minimize reflection of energy back from the oven into the wave guide and the magnetron 12. Thus, the energy is directed generally into the interior of the oven .11 through an opening 17 in the rear wall thereof. Unlike conventional reflecting means, the means 16 is adapted to be moved at an angle with respect to a rear wall 18 of the oven.

The wave reflecting means 16 comprises a bimetallic element 19 of the conventional heat-up and cool-down type and an external, resistance heating element 21 mounted in close proximity to the bimetallic element. The element 19 is capable of deflecting in one direction in response to a rise in temperature of the external resistance heating element, the rise in temperature causing heat to be transferred to the bimetallic element 19. It will be understood that the bimetallic element may be provided with an internal heating element in lieu of the external one.

Energization of the heating element 21 is designed to be periodic, such that, in the deenergized state thereof, the bimetallic element 19 will be permitted to cool down, thereby causing deflection in a direction opposite to that experienced during the heat-up portion of the cycle.

Periodic energization of the heating element 21 is accomplished by means of a cycling control 22 which may be of any conventional type, for example a pair of cam actuated contact arms (not shown) which are open and closed in a predetermined manner. A control knob 23 is provided to connect the control 22 with the power source for the range 10. The cam (not shown) may, once it starts, rotate continuously .or it may be stopped by suitable means during the cool-down cycle of the bimetallic element 19. To obtain optimum results the bimetallic element 19 is mounted in cantilever fashion by means of screws 26, to the rear wall 18 of the oven, adjacent the opening 17. This allows the surface 16 to expand and contract freely in the end of the Wave guide 13. A cover 24 made from any suitable material, for example, glass, is provided to protect the wave reflecting means 16 from vapors from within the oven which would otherwise condense on the bimetallic element 19, necessitating cleaning thereof. A pair of brackets 27, suitably secured to the inside of the rear wall 18, serve to hold the cover over the opening 17 to thereby seal off the wave guide from the interior of the oven.

While there has been shown and described what is at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangements shown and described and it is intended to cover in the appended claims all such modifications as fall Within the true spirit and scope of the invention.

What is claimed is:

1. Heating apparatus, comprising a source of electromagnetic energy, a metallic enclosure, means including a temperature responsive element for transmitting said electromagnetic energy from said source to said enclosure, means adapted to vary the temperature of said temperature responsive element, the position of said element being changed With respect to the direction of said energy upon change in its temperature, whereby said element is effective to produce changes in the distribution of the electromagnetic energy Within the enclosure.

2. In heating apparatus, in combination, a metallic enclosure having an opening, a source of electromagnetic energy, a wave guide coupling energy emitted from said energy source with the interior of said enclosure through said opening, Wave reflecting means in said wave guide adjacent said opening, said reflecting means being movable whereby the energy from said source is reflected into said enclosure in various directions, said wave refleeting means comprising a temperature responsive element.

3. Structure as specified in claim 2 wherein said temperature responsive element is a bimetallic element.

4. Structure as specified in claim 3, including means adapted to effect a variation in temperature of said himetallic element whereby said element is periodically displaced from its normal position in accordance with said variations in temperature.

References Cited UNITED STATES PATENTS 2,909,635 10/1959 Haagensen ,219-10.55

3,211,880 10/1965 Johnson 219-10.55

3,258,574 6/1966 Mooney 21910.55

FOREIGN PATENTS 1,378,280 10/1964 France.

OTHER REFERENCES Kaiser: German application, 1,180,468, printed Oct. 29, 1964 (K1 21b-4/02).

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner. 

